The easiest way to track U.S. postal mail is to go to the USPS website and enter the label or receipt number of the item to be tracked. Tracking information can also be accessed by phone. There are separate numbers for domestic and international tracking.
USPS explains only certain categories of items can be tracked, including priority-mail items, first-class mail parcels, standard-mail parcels, package-services parcels, parcel-select parcels and mail to APO/FPO/DPO (military) locations. Ineligible items include periodicals, most letter-sized items and most mail sent internationally. There is an extra charge to track some categories of mail, and the tracking must be purchased when the item is mailed.
Details of available tracking information include the time the item was handed over to USPS, the processing and departure from each location in the network on the way to its delivery site, its arrival at the final delivery site, its departure with the carrier and the date and time of delivery or attempt at delivery. Tracking only provides information about the progress of the mailed item. It doesn't speed up or otherwise expedite delivery, guarantee a delivery time or make provision for a signature at point of receipt. It does, however, provide a receipt as evidence an item was mailed.